Gurney ~~ long retired. But indeed I find constant refs to this solecism: the last one, which moved me to post the OP, in last week's Spectator.
I think Carroll's jeu of creating the two 'characters' based on the two standard similes, 'Mad As a Hatter' & 'Mad As A March Hare' [which of course simply = a hare in March, their rutting season: there is no such actual being as 'A March Hare'!] a consummate piece of brilliance.
Re 'masterpiece' ~~ it can mean both an apprentice's final qualifying artefact and a fine artist's finest piece - or indeed, any work of art which might be so considered. Few words mean ONLY one thing to the extent that it is incorrect to use them in any other sense, as you perhaps appear to be implying regarding this word.
Sandra ~ a drift, but thanks for reminder that HRH instead of HM for the Queen is another pig-ignorant manifestation that always makes me see red - or do I mean blue?